Growth depression problems in young chickens, known in the poultry production industry by various terms such as “stunting”, “runting-stunting” or “uneven growth” syndrome, result in considerable economic costs for affected farms. Such growth depression has been associated with infections with a variety of viruses including rotaviruses and as yet uncharacterised, small round viruses, known as enterovirus like viruses (ELV). Since the clinical problems caused by specific viruses are ill-defined due to the lack of specific diagnostic tests, it is difficult to accurately estimate the demand for a vaccine to protect against virus-induced growth depression problems.
Virus infections of chickens can be horizontally transmitted from virus that may be contaminating the chicken house; for example, with enteric infections, fecal-oral spread is likely to be common. It is also recognised that vertical transmission of enteric infections via the embryo from virus-infected parent chickens may also occur.
Previous studies (Veterinary Laboratories Agency (VLA), Weybridge), have shown that an enterovirus like virus (ELV), designated FP3, could be detected in the meconium (gut contents) of dead-in-shell chicks, suggesting that this ELV was infecting the embryo and was vertically transmitted from infected parents [Spackman et al. 1984].
Enterovirus-like viruses include picornaviruses, astroviruses, caliciviruses and the like and small non-enveloped spherical viruses which replicate in the cytoplasm. They have an RNA genome and are stable at pH3. Several ELVs which are antigenically distinct from each other have been suggested to cause growth depression in avians.